Side blow molding apparatus and method

ABSTRACT

A side blow molding apparatus of ( 100 ) includes upper guide rails ( 106 ) and lower guide rails ( 108 ). The apparatus ( 100 ) includes a side blow device ( 110 ) having a blow pin assembly ( 112 ) and an inner support assembly ( 114 ). The blow pin assembly ( 112 ) includes a blow pin driver ( 116 ) formed as a cylinder ( 118 ). The blow pin assembly ( 112 ) also includes a blow pin ( 122 ) connected to a shuttle system ( 124 ) which, in turn, is connected to the cylinder ( 118 ). The shuttle system ( 124 ) operates so as to move the blow pin ( 122 ) in a linear manner. The inner support assembly ( 114 ) includes an inner support driver ( 138 ) connected to an extender ( 144 ). The inner support driver ( 138 ) extends and retracts the extender ( 144 ) for raising and lowering the inner support ( 142 ). The blow pin ( 122 ) is positioned on the shuttle system ( 124 ) so that the pin ( 122 ) can be shuttled in and out of a parison during the blow molding process.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to apparatus and methods for forming plasticarticles and, more particularly, to apparatus and methods employingprinciples of blow molding.

2. Background Art

Blow molding technology associated with the forming of relativelyhollow, plastic articles is often referred to as “extrusion blowmolding.” Basic principles of extrusion blow molding technology formaking hollow thermoplastic shapes are described in the Modern PlasticsEncyclopedia 1979, 1980, beginning on page 230. The text of thispublication is incorporated herein by reference.

In brief summary, known extrusion blow molding technology for formingthermoplastic articles utilizes molten plastic which is extrudeddownwardly within a blow molding apparatus, in the form of a parison. A“parison” can be characterized as being typically cylindrical in shapeand formed of plastic. Once the plastic has been extruded into the formof the parison, the blow molding apparatus can close a mold around theparison. When the mold has been appropriately closed, air can beinjected and forced into the parison, which is characterized as “blowmolding” plastic. As the air is being forced inside of the parison, thecavity formed by the parison in the mold is pressurized. The moltenplastic is therefore forced against the outer walls of the mold.

When the plastic article to be formed is sufficiently cooled, thearticle can be ejected from the mold. It should be noted that with thisprocess, the inner wall of the article (formed inside of the parison) isformed only by the pressurization of the cavity. This inner wall cantherefore vary relatively significantly by either the thickness of theparison, or the shape of the article. Accordingly, known blow moldingapparatus and methods associated therewith can have certaindisadvantages when customers for the plastic articles require relativelytight tolerances on the inner walls of the plastic articles.

As previously stated, various apparatus and methods have been developedrelating to concepts associated with blow molding plastic articles. Toovercome the problem of providing for relatively tight tolerances forinner walls of the blow molded articles, it is known to use a blowmolding technique referred to as “bottom blow” technology. This andother blow molding apparatus and methods known in the prior art aredescribed in the following references.

More specifically, Maass, U.S. Pat. No. 3,048,891, issued Aug. 14, 1962,discloses a blow molding machine and associated process for forminghollow articles from organic plastic material. In particular, the Maasspatent discloses the concept of insertion of coring pins 66 into theends of a parison, before entry of a blow pin or a needle 74 into theside. This function is performed so as to form a final article having awalled core structure.

Peters, U.S. Pat. No. 3,973,896, issued Jan. 24, 1989, discloses theconcept of a blow molding apparatus with a mandrel carried by portionsof the mold, and movable between extended or retracted positions. Themandrel has a free end with a vacuum surface area portion. The free endis engageable with the parison when the mandrel is in the extendedposition. A blow needle is reciprocally mounted in the mandrel.Insertion of the needle into the parison is facilitated by the parisonbeing held against the end of the mandrel by the vacuum.

Troutman, et al, U.S. Pat. No. 5,078,948, issued Jan. 7, 1992, disclosesa particular blow needle structure having a tubular portion and acutting tip atop the tubular portion. The cutting tip includes three ormore blades terminating in a point. The tubular portion includespassages which communicate with the source of pressurized fluid. The“arrow head” needle penetrates the parison and forms “flap sections” inthe parison. The needle tip pushes the flap sections inwardly within theparison.

Omi et al, U.S. Pat. No. 6,537,056, issued Mar. 25, 2003 is alsodirected to a specific structure for a needle blow nozzle. The needleblow nozzle includes a tubular body with a needle portion, needlecenter, slopes and nozzle holes. The needle is laterally inserted into aparison for jetting air into the interior of the parison. The slopes areformed so as to extend from the needle center toward an outer peripheralsurface of the tubular body. In this manner, edges are provided whichextend at an acute angle, and the nozzle holes are formed in the needleportion.

Other patent references found in our search are directed to severalother concepts associated with blow molding assemblies and processes.For example, Hahn, U.S. Pat. No. 4,028,034, issued Jun. 7, 1977, isdirected to a method and apparatus for blow molding plastic, where themold has a quadrasectional configuration. Particles are extruded from anextrusion unit 10 as a tubular configuration 16 for introduction withinthe mold 18. The article is blow-molded using an expanded fluidintroduced through a hollow needle 32 at the side of the mold. Thearticle is severed into two portions through the use of a hot wire.

Roggenburg, Jr., et al, U.S. Pat. No. 4,332,750, issued Jun. 1, 1982,discloses a blow molding apparatus having a gate which connects the blowmolded hollow shapes to the parison. Subsequent degating of the shapesis provided by ultrasonic mechanical vibrations applied to the gates.

Peters, U.S. Pat. No. 4,799,876, issued Jan. 24, 1989, is primarilydirected to a blow needle configuration. The needle includes a sealingmember which surrounds the blow needle. During inflation of the parison,projections come into sealing contact with the exterior surface. Thisconcept is disclosed as preventing leakage of blow gas from the interiorof the parison around the blow needle.

Raboin, U.S. Pat. No. 6,090,339, issued Jul. 18, 2000, is directed to aprocess for manufacture of a blow-molded plastic extruded product havinga specific configuration. The blow mold apparatus includes a pair ofmold sections which are closed along a linear direction of travel. Whenclosed, they form a mold cavity which includes a narrow sectionextending in the direction of travel. This section has a width which isless than approximately twice a wall thickness of the parison. As themold sections close, they sever and enclose a segment of the parisonwithin the mold cavity, and shear a double-wall section of the parisoninto the narrow section. This forms a reinforcing flange on theresultant product.

Hutchins, U.S. Pat. No. 6,440,353, issued Aug. 27, 2002, is directedexpressly to a vacuum forming method for twin-sheet vacuum forming partsin a vertical orientation. With twin or dual-sheet forming, two sheetsof plastic sheet are parallel-laid in a horizontal fashion, and heatedto a predetermined temperature. In the Hutchins method, two parallelsheets of plastic synthetic resin are clamped together in a verticalorientation to a clamping tray. The sheets directly contact each otherabout the perimeter of the tray. Air is then blown between the sheets soas to create the appropriate hollow cavity, and the sheets are heated tomolding temperatures in a vertical orientation. A vertically-orientedsplit mold is then opened, with the mold cavities having a contour whichconforms with configuration of the desired article. The two parallelsheets are then disposed between the opposing mold cavities of the splitmold, and negative pressure is applied to vacuum section holes providedin the mold cavities. The split mold is then closed so as to form a“pinch off” around the perimeter of the hollow cavity. In this manner, amolded hollow part is formed which is still disposed within the clampingtray. A blow pin is then inserted into the hollow cavity for blowingcompressed air into the cavity to push the parallel sheets against themold cavities. The molded part is then cooled to a set point, thevertically-oriented split mold is opened, and the clamping traywithdrawn.

Ohno, et al, U.S. Patent Application Publication No. 2006/0204606,published Sep. 14, 2006, is directed to cooling processes associatedwith blow molding methods and apparatus. More specifically, upper andlower portions of a parison are forcibly cooled, using upper and lowerholes of respective needle blow nozzles. The metallic mold is cooledspecifically by a cooling apparatus within the mold. The upper clampportion and lower clamp portion formed on the upper and lower portionsof the parison, respectively, are cooled by air which passes onlythrough an upper discharge hole formed on the upper needle blow nozzleand a lower discharge hole formed on the lower needle blow nozzle.

Nemoto, U.S. Patent Application Publication No. 2008/0038497, publishedFeb. 14, 2008, is directed to a blow molding die assembly and associatedmethods for manufacture of resin hollow bodies. One of the dieassemblies comprises a pair of main dies which are formed with adividable cavity, by closing open end surfaces with each other. A pairof slide dies is disposed outside of the main pair of dies, and haveabutting portions that move between first positions where the abuttingportions project outwardly from the open end surfaces, and secondpositions where the abutting portions are located inward of the open endsurfaces of the main dies. A method for manufacturing resin hollowbodies uses the aforementioned die assembly with a series of opening andclosing steps.

As earlier stated, problems exist with respect to a number of the priorart apparatus and methods associated with blow molding technology whenthe formed article requires relatively tight or small tolerances withrespect to the thickness of the parison or the shape of the articleitself. For example, and as earlier stated, it is known to employ whatis characterized as a “bottom blow” process which provides at least someimprovement over other known processes for generating blow moldedplastic articles having relatively tight tolerances on the inner wallsof the articles. Assuming that the article to be formed includes a neckportion, the bottom blow process involves dropping the parison over amachine and blow pin. The blow pin remains inside the mold, and formsthe inner diameter of the neck of the article. Such a process couldpossibly be applied to blow molded articles such as necks of engineresonators. Such engine resonators utilize what is often referred to as“Helmholtz resonance,” which is essentially the phenomenon of airresonance within a cavity. Airboxes and other components of internalcombustion engines use the principles of Helmholtz resonance for soundmuffling and other purposes. In the fabrication of engine resonators,the dimensions of the necks of the resonators are of particularimportance in proper operation. Accordingly, tight tolerances arerequired on the “inner diameter” or inside wall of the resonator necks.In fact, tolerances on the order of +/−0.5 millimeters may beconsidered. However, with bottom blow processes, it is often difficultto accurately form a desired length and shape of various types ofresonators and other blow molded articles. In particular, for certainshapes and article lengths, the required parisons for such articles tobe bottom blown would be extremely difficult to program into a moldingapparatus.

SUMMARY OF THE INVENTION

In accordance with the invention, a method for forming plastic articlesutilizes the principles of blow molding and employs a blow mold and ablow pin. An operational sequence is initiated, with the blow mold in anopen position and the blow pin in a retracted or home position. Aparison is then extended over an inner support. A blow pin driver isactivated, and causes a shuttle system of a side blow device to operate,so as to extend the blow pin sufficiently to pierce the parison.

The inner support guide can then be retracted, and the blow mold can beclosed. A forming and cooling cycle can then be initiated and operated.Following the cycle, the blow pin can be retracted and the resultantplastic article can be ejected. The extender can then be extended andthe inner support device can be repositioned to an initial position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawings, inwhich:

FIG. 1 is a perspective view of a side blow molding apparatus, having aside blow pin assembly in accordance with the invention; and

FIG. 2 is a perspective and essentially “stand alone” view of the sideblow device forming a part of the side blow molding apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The principles of the invention are disclosed, by way of example, in aside blow molding apparatus 100, as described herein and illustrated inFIGS. 1 and 2. A principal advantage of the side blow molding apparatus100 in accordance with the invention is that it can be utilized to blowmold plastic articles where relatively tight tolerances on thedimensions of the inner walls of the articles are required. Such blowmolded articles can include, for example, engine resonator necks wheretight tolerances need to be held with respect to the dimensions of theinside wall of the necks. Because of the lengths and shapes of certainengine resonators and other blow molded articles, it is substantiallydifficult to use the bottom blow process.

In part, the apparatus 100 and other apparatus in accordance with theinvention provide for the molding of articles which cannot be bottomblown, to be formed with a relatively conventional parison, and yetstill be capable of forming an inside wall having dimensions withinrelatively tight tolerances. As earlier described, the reference to thedimensions of the inside wall may be referred to herein as the “ID” or“inside diameter.”

More specifically, with the use of side blow technology in accordancewith the invention, the geometry of the articles to be molded is notsubstantially restricted, in the manner in which such geometry isrestricted when bottom blow technology is utilized. Still further, withside blow technology in accordance with the invention as describedherein, multiple inner features can be formed using apparatus andmethods in accordance with the invention.

Turning specifically to the drawings, FIG. 1 illustrates a perspectiveview of the major components of the side blow molding apparatus 100,which can be used with components in accordance with the invention. Theside blow molding apparatus 100 includes a conventional base frame 102,having legs 104 which can be supported on any type of appropriatesurface. Extending linearly through the apparatus 100 are a set of upperguide rails 106 and lower guide rails 108. These rails 106, 108 areutilized to appropriately guide various sliding components used with theapparatus 100.

It should be noted that the side blow molding apparatus 100 alsoincludes a number of other various components. Many of these componentsare conventional in nature and will not be described in detail herein.Such conventional components of the side blow molding apparatus 100 aredescribed in various prior art references, including those referencescited in the section of this application entitled “Background Art.” Forexample, such components can include a conventional pneumatic systemhaving various types of hoses, valves and other components, including ahigh pressure air source. In addition, the molding apparatus 100 caninclude cooling devices for purposes of cooling the parison aftercompletion of the molding process. In addition to these components,computer apparatus, including programmable controllers, can be utilizedto appropriately sequence the various process steps associated with theoperation of the side blow molding apparatus 100. The automatedtechnology can include numerical control machines and various othertypes of computerized apparatus.

The novel concepts of the side blow molding apparatus 100 in accordancewith the invention are found primarily embodied within the structure andoperation of a side blow device 110, primarily shown in a “stand alone”perspective view in FIG. 2. The side blow device 110 can becharacterized as comprising two principal component assemblies. Thesecomponent assemblies include what is characterized as a blow pinassembly 112 and an inner support assembly 114, both of which are againshown in FIG. 2 as part of the side blow device 110. The blow pinassembly 112 can be characterized as being structured on a slide system,with the slide system essentially performing the function of shuttling ablow pin in and out of the molding area. Correspondingly, the innersupport assembly 114 can be characterized as being constructed on an aircylinder apparatus, with the air cylinder apparatus raising and loweringthe inner support assembly 114.

More specifically, the blow pin assembly 112 includes a blow pin driver116. The blow pin driver 116 can be formed as a cylinder 118 mounted ina stationary manner on a cylinder base 120. Within the cylinder 118 canbe a cylinder piston (not shown) which can be operated by appropriatepneumatic controls (not shown) so as to appropriately move the piston.

In addition to the blow pin driver 116, the blow pin assembly 112includes the blow pin 122, again as shown in FIG. 2. The blow pin 122 isconnected to a shuttle system 124 which, in turn, can be connected tothe cylinder 118. The shuttle system 124 operates so as to move the blowpin 122 in a linear manner. The blow pin 122 and the shuttle system 124rest in part on a shuttle base 132. The entirety of the blow pinassembly 112 rests on a lower base mounting bracket 126. The basemounting bracket 126 is connected to an intermediate bracket 128 mountedabove the mounting bracket 126. Correspondingly, an upper bracket 130 ismounted intermediate the intermediate bracket 128 and the cylinder base120. All of the mounting bracket and base components remain stationaryduring operation.

Turning to the inner support assembly 114, and again primarily withrespect to FIG. 2, the inner support assembly 114 includes an innersupport mounting bracket 134 at the lower portion thereof. The mountingbracket 134 is connected to a connecting bracket 136. In turn, theconnecting bracket 136 is connected in a stationary manner to the basemounting bracket 126 previously described herein. The inner supportmounting bracket 134 mounts an inner support driver 138. The innersupport driver 138 can be in the form of an air cylinder (notspecifically shown), with an interconnected pneumatic control system(not shown). The inner support driver 138 is connected through avertically disposed extender 144 to an upper driver bracket 140. Inturn, the upper driver bracket 140 is connected to an inner support 142having the shape and configuration as primarily shown in FIG. 2. Theinner support 142 includes an upper section 146 and a lower section 148.In operation, the inner support driver 138 can be utilized to extend andretract the extender 144 which, in turn, will raise and lower the innersupport 142. In summary with respect to the entirety of the foregoing,the blow pin 122 is built on a shuttle system 124 which shuttles the pin122 in and out of the parison. Correspondingly, the inner support 122 ispositioned on an inner support driver 138 which can include an aircylinder or the like so as to raise and lower the inner support assembly114.

The operation of the side blow molding apparatus 100 in accordance withthe invention will now be described. It should again be noted that thenovel concepts associated with the side blow technology provide anadvantage in that these concepts permit blow molded articles that cannotbe bottom blown to be formed with a conventional parison and still beable to form the inner diameter of article components having extremelytight tolerances. The principal concept associated with this technologyis the concept of piercing the parison with the blow pin, and with theblow pin staying inside the parison as the mold closes. This functionthen forms the inner diameter of the article neck. It should beemphasized that the use of the inner support is critical to theoperation of the system. That is, without the inner support, the blowpin is unlikely to be able to pierce the parison.

In describing the operation of the apparatus 100, reference again ismade to FIG. 1, which illustrates the blow mold 150 and the parison 152.In an initial state, to begin an operational sequence, the mold 150 isin an open position, and the blow pin 122 is in a retracted or “home”position. Correspondingly, the inner support driver 138 and innersupport 142 are in an extended and ready position. At this time, theapparatus 100 then operates to extrude the parison 152. The parison 152will drop over the inner support 142.

When the parison 152 has been fully extruded, the blow pin driver 116can be activated. This will cause the shuttle system 124 of the sideblow device 110 to operate so as to extend the blow pin 122 in a mannersuch that the blow pin 122 will pierce the parison 152. When the blowpin 122 has been fully extended into the parison 152, the inner supportguide is then retracted. The blow mold 150 is then closed. At this time,it should be emphasized that although the mold 150 is closed, the blowpin 122 remains inside the parison 152.

A forming and cooling cycle is then initiated, using principles of blowmold cooling well known in the art. At the end of the cooling cycle, theblow pin 122 can be retracted to its retracted or home position. Withthe pin 122 retracted, the finished part can be ejected from the sideblow molding apparatus 100. At this time, the inner support driver 138can extend the extender 134 and inner support 142, with the extensionpositioning the inner support 142 to its “ready” position. The foregoingcycle can then be repeated for another blow molded article.

Again, it should be emphasized that with the use of the side blow device110 and the principles of operation associated therewith, the partgeometry of the article to be molded does not particularly restrict theuse of the process described herein. This is a problem with respect tothe use of bottom blow technology. Also, and as earlier stated, multipleinner features can be formed using this process in accordance with theinvention.

It will be apparent to those skilled in the pertinent arts that otherembodiments of blow molding apparatus in accordance with the inventioncan be designed. That is the principles of a blow molding apparatus inaccordance with the invention are not limited to the specific embodimentdescribed herein. Accordingly, it will be apparent to those skilled inthe art that modifications and other variations of the above-describedillustrative embodiment of the invention may be effected withoutdeparting from the spirit and scope of the novel concepts of theinvention.

1. A method for forming a plastic article using the principles of blowmolding and employing a blow mold and blow pin, said method comprising:initiating an operational sequence with said blow mold in an openposition and said blow pin in a retracted or home position; extruding aparison over an inner support; activating a blow pin driver, and causinga shuttle system of a side blow device to operate so as to extend saidblow pin sufficiently so as to pierce a side of said parison; retractingan inner support extender, thereby lowering an inner support; closingsaid blow mold; initiating and activating a forming and cooling cycle;retracting said blow pin; ejecting a resultant plastic article; andrepositioning said extender and said inner support to initial positions.